Pretreatment primary tumor SUVmax on ¹⁸F-FDG PET/CT images predicts outcomes in patients with salivary gland carcinoma treated with definitive intensity-modulated radiation therapy

Purpose The aim of this study was to investigate the prognostic significance of 18 F-FDG uptake in salivary gland carcinoma (SGC) patients treated with definitive intensity-modulated radiation therapy (IMRT). Methods We retrospectively examined 46 SGC patients who received pretreatment 18 F-FDG PET/CT and definitive IMRT between 2007 and 2014. Most tumors were located in the minor salivary glands (n = 35 [76%]). Forty-six percent (n = 21) of the participants had unresectable disease. The median radiation dose was 72 Gy. Treatment outcomes were examined in relation to clinicopathologic parameters and pretreatment primary tumor SUVmax on 18 F-FDG PET/CT. Results After a median follow-up of 54 months, the 5-year locoregional progression-free survival (LRPFS), distant metastasis-free survival, progression-free survival (PFS), and overall survival (OS) rates were 77%, 75%, 63%, and 61%, respectively. The median primary tumor SUVmax was 7.4 (range, 2.3-23.6), and the optimal cutoff value that maximized the prognostic significance for 5-year PFS was 7.4 (P = 0.006). Patients with a high SUVmax (≥7.4) had significantly lower 5-year LRPFS (P = 0.007), distant metastasis-free survival (P = 0.046), and OS (P = 0.013) rates than those with a low SUVmax (<7.4). Multivariate analyses identified SUVmax as the only independent predictor of LRPFS (P = 0.023) and PFS (P = 0.003), whereas both the performance score (P < 0.001) and SUVmax (P = 0.022) were independently associated with OS. Conclusions Pretreatment primary tumor SUVmax on 18 F-FDG PET/CT predicts treatment outcomes in SGC patients. Definitive IMRT is an effective treatment strategy when organ function and cosmesis need to be preserved.